No problem, I see your point.

Personally I haven't seen or read of any ignition system shorting out, but it's not really something that you're going to hear about on a regular basis. If it were to happen, the person would probably lose the plane, if it was piggy-backed on the receiver battery and would go down as "radio failure" or a "bad battery."

Another thing that could happen that I didn't mention, is a high current draw situation draining the flight pack. For instance, if the spark plug was worn or incorrectly gapped (i.e. excessive gap), that would cause the amp draw to increase quite a bit, and could drain the pack at a faster rate than expected.

This is all strictly opinion on my part, but again, why take the chance when batteries are so inexpensive?